The present invention relates to a differential gear for vehicles, in particular for four wheel drive vehicles.
Four wheel drive vehicles include a transfer case, which splits the torque, delivered by the engine, between the front axle and the rear axle. In addition, each of the two axles also requires an axle gear, that is a differential gear, which makes it possible to balance the rotational speed between the wheels on the inside and the outside of the curve when cornering. Frequently, modern four wheel drive vehicles must satisfy the requirement that the torque can be split in a totally variable manner between the front axle and the rear axle. Whereas the axle gear of conventional vehicles acts as the “torque balance”, that is, the same torque is always transferred to the two output shafts, the trend is to demand, especially in the case of four wheel drive vehicles, that the torque be split in a tailored manner, that is, adapted to the specific driving situation, between the two wheels of an axle.
The object of the invention is to provide a differential gear, which is intended for vehicles and which makes possible an independent splitting of the introduced torque between the two output gears, that is suitable especially for four wheel drive vehicles and makes possible an independent splitting of the current torque between the front and rear axle, and can be shifted into an “overdrive mode”.
This object is achieved by a differential gear, including a drive, in particular a bevel drive pinion, and a left output shaft and a right output shaft. A rotatably mounted basket is driven by the drive, and is coupled with the left output shaft by way of a left superposition gear and with the right output shaft by way of a right superposition gear. A double planetary gear set exhibits an internal geared wheel, which is mounted on the basket, as well as radially outer planet gears, which mesh with the internal geared wheel. Radially inner planet gears mesh with the radially outer planet gears and with a gearwheel, which is connected to a first of the two output shafts. A planet carrier is provided on which the radially inner and the radially outer planet gears are mounted. The planet carrier can be coupled with the second of the two output shafts by way of a clutch. Advantageous embodiments are further developments of the invention are described herein.
The starting point of the invention is a differential gear with a drive, which can be formed, for example, by a bevel drive pinion. The drive forms the “input” of the differential gear. Of course, the differential gear has two outputs, that is, a left output shaft and a right output shaft as well as a rotatably mounted “basket”, which is driven by the “drive”. The basket is coupled with the left output shaft by way of a left “superposition gear” and with the right output shaft by way of a right superposition gear. Furthermore, in contrast to conventional differential gears, the differential gear exhibits a “double planetary gear set”. The double planetary gear set in turn exhibits an internal geared wheel, which is mounted on the basket, as well as radially outer planet gears, which mesh with the internal geared wheel, and radially inner planet gears, which mesh with the radially outer planet gears and with a gearwheel, which is connected to a “first” of the two output shafts, and a planet carrier, on which the radially inner and the radially outer planet gears are mounted. The planet carrier is mounted in a rotatable manner with respect to an axis that is formed by the two output shafts. The planet carrier can be coupled with the “second” of the two output shafts by use of a clutch.
Preferably, each of the two superposition gears is assigned a superposition gear clutch, which in each case is provided for the purpose of opening or closing the assigned torque path between the basket and the assigned output shaft. The results of having these clutches, in total three, which are integrated into the differential gear, are various operating states, which are explained below in detail in connection with the drawings.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.